Howitzer Motor Carriage M8
|75 mm Howitzer Motor Carriage M8|
75 mm Howitzer Motor Carriage M8 on display at the Musée des Blindés.
|Place of origin||United States|
|Used by||See Users|
|Designer||U.S. Army Ordnance Department|
|Manufacturer||Cadillac division of General Motors|
|Produced||September 1942–January 1944|
|Specifications (75 mm Howitzer Motor Carriage M8)|
|Weight||34,600 lb (15.69 metric tons) combat weight|
|Length||16 ft 4 in (4.98 m) with sand shields|
|Width||7 ft 7.5 in (2.32 m) with sand shields|
|Height||8 ft 11 in (2.72 m) over antiaircraft machine gun|
|Crew||4 (Commander, gunner, driver, assistant driver/loader)|
|Armor||0.375 to 1.75 in (9.5 to 44 mm)|
|75 mm Howitzer M2/M3 in Mount M7
|.50 caliber (12.7 mm) Browning M2HB machine gun
|Engine||Twin Cadillac Series 42 inline 6 cylinder 4-stroke gasoline engine
220 hp (164 kW) total at 3,400 rpm; 110 hp (82 kW) per engine
|Power/weight||14.02 hp/metric ton|
4 speeds forward, 1 reverse
|Suspension||Vertical volute spring suspension (VVSS)|
|Ground clearance||14 in (0.35 m)|
|Fuel capacity||89 US gallons (340 liters)|
|100 mi (160 km) on road|
|Speed||36 mph (58 kph) on road|
|Controlled differential, steering levers|
Development and design
The first design for a close support howitzer on an M5 tank chassis was the T41, which had the howitzer in the hull front. This did not progress past the mock-up stage as the crew would not have been sufficiently protected and design work started on the T47. It was developed on the chassis of the then-new Light Tank M5 (Stuart VI). The prototype was designated the 75 mm Howitzer Motor Carriage T17E1 It had the standard M5 turret removed and replaced with a larger open-topped turret; as a result, the drivers' hatches had to be moved from the hull roof to the glacis plate. After a mock-up had been produced, it was ordered into production as the 75 mm Howitzer Motor Carriage M8. The M8 was based upon the Light Tank M5, but incorporated several changes. Like the Light Tank M5, the M8 had a crew of four; commander, gunner, driver, and assistant driver/loader. When the M8 was in action, the commander positioned himself at the antiaircraft machine gun and directed his crew, the gunner sat in the turret on the right side of the howitzer, the assistant driver/loader moved up from his seat in the right front hull, and the driver stayed at his position.
Due to the usage of a new turret, the crew hatches in the hull roof for the driver and assistant driver/loader were deleted and replaced by a pair of vision flaps in the glacis. Since the glacis hatches were too small to disembark through, these two crew members had to leave the vehicle through the open-topped turret. The driver and assistant driver/loader were provided with periscopes for visibility. In November 1944, the Ordnance Department gave the M8 the name General Scott, after American general Winfield Scott.
As the M8 was based upon the Light Tank M5 (itself a descendant of the Light Tank M3) it had relatively thin armor. The lower hull armor ranged from 1 in (25 mm) to 1.125 in (28.6 mm) on the sides to 1.75 in (44 mm) on the lower front and 1.0 in (25 mm) on the lower rear. The lower hull sides were vertical, while the lower hull front was sloped at 18 degrees from the vertical, and the lower hull rear, which protected the engine and radiator, was sloped at 17 degrees from the vertical. The hull floor ranged from 0.5 in (13 mm) thick at the front to 0.375 in (9.5 mm) thick at the rear. The glacis plate of the M8 was sloped at 45 degrees from the vertical and was 1.125 in (28.6 mm) thick. The upper hull sides, like the lower hull sides, were vertical and 1.125 in (28.6 mm) thick at the front, thinning to 1 in (25 mm) thick at the rear. The upper rear hull was a vertical plate, 1 in (25 mm). The plate sloped at 50 degrees for a short distance before it met the hull roof, which was uniformly 0.5 in (13 mm) thick, and flat.
The turret of the M8 was of cast steel. It was 1.5 in (38 mm) thick at the front, which was rounded, sloping from 0 to 63 degrees from the vertical. The sides and rear were 1 in (25 mm) thick and sloped at 20 degrees from the vertical. The cast gun shield which covered the barrel of the 75 mm Howitzer M2/M3 was 1.5 in (38 mm) thick and rounded.
The armament of the M8 consisted of a new open-topped turret armed with a 75 mm M2 howitzer, later a 75 mm M3 howitzer. The M8 carried 46 rounds of 75 mm ammunition; 11 rounds at the right rear of the fighting compartment, 20 rounds at the left rear of the fighting compartment, 9 rounds in the left hull sponson, and 6 "ready" rounds stored between the driver and assistant driver's positions. The most common types of ammunition carried were the M89 white phosphorus shell and the M48 high explosive shell. Unlike the standard M5 light tank, the M8 featured no hull-mounted or coaxial Browning M1919A4 .30 caliber machine gun. A Browning M2HB .50 caliber machine gun with 400 rounds was mounted on the right rear corner of the turret for local defense and anti-aircraft purposes. For self-defense, the vehicle driver was provided with a Thompson submachine gun, while the other three crew members were issued M1 carbines.
|Month||Number built||Serial number(s)||Registration number(s)|
The 75 mm Howitzer Motor Carriage M8 was assigned to the Assault Gun Troops of Cavalry Reconnaissance Squadrons in order to give them close support against enemy fortified positions. The high elevation (40 degrees) of the howitzer was useful for hitting enemies emplaced on the sides of hills. The M8 was used in the Italian Campaign, the Western Front, and in the Pacific Theater of Operations by the US Army and on the Western Front by the French Army. It was also used by the French Union and State of Vietnam during the First Indochina War. It stayed in French service until the 1960s and saw service in Algeria.
- 75 mm Gun Motor Carriage M8A1: A lightweight tank destroyer prototype that used an M5A1 light tank hull. The M8's turret was paired with a 75 mm gun M3 as used on the M4 Sherman tank. The project was later cancelled with the development of the M18 Hellcat.
- United States - U.S. Army
- France - French Army
- South Vietnam - Army of the Republic of Vietnam (ARVN)
- Cambodia - Khmer National Army (FANK)
- Kingdom of Laos - Royal Lao Army
- Republic of China - Republic of China Army (ROCA)
- Tunisia - Tunisian Army
- Landing Vehicle Tracked (Armored) 4) — an LVT(A)1 rearmed with the turret of the 75 mm Howitzer Motor Carriage M8
- "M8 Scott (Howitzer Motor Carriage M8) 75mm Self-Propelled Howitzer (SPH) (1942)". MilitaryFactory. October 17, 2014. Retrieved February 5, 2015.
- Chamberlain and Ellis (1969) British and American Tanks of World War II p96
- War Department Armored Command Field Manual 17-69 Crew Drill, Service of the Piece, and Gunnery (75-MM Assault Howitzer on Motor Carriage M8), dated 30 November 1943, pp. 3-5
- War Department Armored Command Field Manual 17-69 Crew Drill, Service of the Piece, and Gunnery (75-MM Assault Howitzer on Motor Carriage M8), dated 30 November 1943, p.4
- Ordnance Department Armored, Tank, and Combat Vehicles 1940-45, page 11 (1 May 1945)
- Official Munitions Production of the United States by Months, July 1, 1940 - August 1, 1945, page 231 (War Production Board and Civilian Production Administration, 1 May 1947)